midrange bog, not jetting related

[BryanMcc]

here is what the problem is. every ride at some point my bike will act up in a big way. here is what i have noticed so far. problem is very intermittant.
1) big load on engine (long uphill sections) make the bog worse, sometimes to the point it wont clear out. mainly on an upshift where i come off the pipe slightly.
2) long straightaways with sustained upper throttle the bike will bog again midrange once i letoff and come back on the throttle.
3) stopping and shutting the bike off makes it go away for a minute, at least untill i get on the throttle again and let off then get back on it. ( runs fine through the gears for the first time its after i let off the throttle and go to get back on it)
4) when the bike rattles ( i think power valve rattle) there will be no bog, once the rattleing quiets down it will with out a doubt bog.
5)the mapping switch in rain mode makes it much worse
6)jetting is as follows and plug chops look great (only doing plug chops with the bike running normally. 165-168 main, JD red in number 2, 40 pilot, a/s 1 and 3/4 out, 4 to 7k feet and 60 to 90 degrees
7) when the bike starts acting up the exhaust note chages and it seems like there is alot of noise in the expansion chamber. very distict change

my thoughts were a gummed up power valve, but i yanked it out tonight and there was only a little carbon built up. right now i have transmission side cover off. how do i make sure i don t have a ball for the PV controller dislodged? im going to check preload on the PV spring and button it back up, also make sure the rod isnt binding or catching anywhere. anything else i should check while im in there? i only want to buy gaskets once LOL. I have a race coming up oct seventh and would rather race my gas gas instead of the husky because the mikuni carb in the husky is a turd to jet. Thanks for the help! GG rider rules, so much knowlege on here!

 

[Jakobi]

Hmmm.. Hmmm hmmm.. I feel like I've read these symptoms before..

Double triple check that crud is not in the tank making its way into the carb. Put a filter between the two. Doubt its this but its good practice.

Check the breathers and check valves for the carb and the fuel tank.

Power valve. The drums that run in the cylinder can get a small carbon build up and cause sticking. It doesn't take much. To test remove the actuator arm from the powervalve and the allen bolt that stops the plate rotating too far. You should then be able to cycle the valve 360 degress both forward and backwards smoothly. If it jags forward to back you have your issue. Also check the side play and see how this affects the rotation of the pv.

Electrically, I know nothing about electrics but spark plugs, plug cap, coil. The map switch making a difference makes my ears prick up to this.

 

[desertgasser300]

X2 on the PV sticking. Had the same sysmptoms you are describing on my 97'. I went right for the PV and sure enough it was sticking. Pulled it out and and scrapped all the carbon off and then wire brushed it....BINGO bikes runs great again!

 

[GMP]

It does sound PV related to me. A simple diagnosis before disassembly would have been removing the right side PV cover and observing the PV operation through the RPM range. Now that it is apart this impossible.

Verify that the cylinder components move smoothly and easily. The PV should close under the weight of the flapper if everything is clean and carbon free.

If a ball were dislodged it would prevent the PV governer from returning to the "home" position, and the PV would be stuck open somewhat at lower RPM. Balls become dislodged from manually moving the governer with the engine off (by pulling on the rod), causing them to fall out of their ramps. Lay the bike on its side or remove the governer to check. You can sometimes reseat the balls with a pick if neccessary without disassembling the governer.

It would not hurt to go through all your connections especially the coil HV wire, although I doubt its the cause of this. The rain mode delays advance so it makes a problem situation worse.

Rest of plan is good.

 

[BryanMcc]

there was some carbon build up on the drums, ill clean them and reinstall tonight. Ill double triple check the carb vents, but i was king of doubting that due to the issue being related to the amount of rattle and the change of exhaust tone. Ill also add a small inline filter in the fuel line.. power valve did feel smooth in its operation before it came apart. If a ball was dislodged wouldnt it run funny ALL the time? the part that confuses the hell out of me is if i shut the bike all the way down it behaves untill im on the throttle hard again and back off. The bog is so bad a 1 to 2 shift of a hill will actually slow me down until i shift back to first, will not get on the pipe. Thanks for the help!

 

[stainlesscycle]

i have had a pv governor issue with the dislodging. when it happened to me, i had no top end, no rev out, bike will just putt around. it will not rev up at all. maybe 3000-4000rpm max..

 

[GMP]

Thats because the ball left the ramp and did not contribute to the inertia of moving the governer, but they can also jam the system from closing.

BryanMCC,

It makes sense to me, its sticking open after being opened hard. Maybe that governer and the bellcrank should come apart and be inspected for anything that would cause it to stick, like a burr. Your in there now anyway.

Whats the history here? New/used bike? Recent work, etc.?

 

[wasp4banger]

there was some carbon build up on the drums, ill clean them and reinstall tonight. Ill double triple check the carb vents, but i was king of doubting that due to the issue being related to the amount of rattle and the change of exhaust tone. Ill also add a small inline filter in the fuel line.. power valve did feel smooth in its operation before it came apart. If a ball was dislodged wouldnt it run funny ALL the time? the part that confuses the hell out of me is if i shut the bike all the way down it behaves untill im on the throttle hard again and back off. The bog is so bad a 1 to 2 shift of a hill will actually slow me down until i shift back to first, will not get on the pipe. Thanks for the help!

You checked the float level in the carb?

 

[Jakobi]

I had my powervalve stick wide open. The bike was gutless and the exhaust tone was so bad I thought I had seriously damaged something. I didn't rev it hard enough to see if it'd get the one pipe it sounded so bad!

As Glenn said an easy test is to run the bike on the stand with the RHS pv cover off and see if it moves as it should.

 

[BryanMcc]

You checked the float level in the carb?

yes float level checked and adjusted, looks good

 

[BryanMcc]

Thats because the ball left the ramp and did not contribute to the inertia of moving the governer, but they can also jam the system from closing.

BryanMCC,

It makes sense to me, its sticking open after being opened hard. Maybe that governer and the bellcrank should come apart and be inspected for anything that would cause it to stick, like a burr. Your in there now anyway.

Whats the history here? New/used bike? Recent work, etc.?

new bike this year, holdover 2010. No recent work other than regualr maint and jetting. Has maybe 100 hours.

 

[Stoby]

sounds like pv but i had an almost similiar prob once , check crank seals if its not the pv .your bikes kinda new for it but.... When i'd get on mine hard itd sometimes bog .my friend noticed occasional excess smoke ,told me.I changed seal prob solved

 

[BryanMcc]

well it will be a bit before i know if cleaning/adjusting the power valve did the trick as i snapped the bellcrank adjuster bolt the sets the preload. heading to go fasters and appalacian offroad for one piece that go fasters doesnt stock. Hopefully this experience will be better than the last with appalacian offroad. Should i change to a metal inpeller while im in there? i have heard some horror stories

 

[Jakobi]

If you're already in there you might as well.

 

[GMP]

Absolutely. Be sure it clears the cover though. The alloy impeller is slightly deeper in the center for more flow, and the covers are inconsistant. I've seen everything from nicely machined to rough cast surfaces. Assemble it in the side cover on the bench and turn by hand to be sure.

 

[Jakobi]

What if it doesn't clear it Glenn? I noticed when I had my cover off last that the plastic impeller had made contact and worn a groove in a section of it. I think the dealer had the waster pump cover off to replace the kick start shaft and only reassembled with liquid gasket. Since installing a real gasket again seems to be fine.

 

[GMP]

I did two things. First I cleaned up the casting and polished the surface to a smooth finnish. This is easy but time consuming. If your cover is machined smooth inside then its no big deal. Next I used a counterbore to take approx .5mm off the rear of the impeller so it clears the cover adequately. Just bolt it together tempoarily and turn it by hand, you will know. These covers really need to be done better. A nice aftermarket part would be a matching impeller/cover like Boyeseen had for some of the 4strokes.

 

[BryanMcc]

all i want for christmas is to ride my broken gasgas

now jakobi's comment about the groove worn in his impeller is making me get up off the couch and go look at mine in the garage to see if mine has damage. now Glenn's comment is getting me back up off couch to go look inside cover. You guys are killing me lol

 

[Jakobi]

Haha my groove wasn't in the impeller It was in the actual cover itself. I was actually quite surprised it wasn't the impeller that wore.

 

[GMP]

What makes me get up off the couch and in the garage is pics of snapped impeller shafts and shattered bearings without an explanation. Not saying its a widespread problem or the cause but its not good for that impeller to contact the cover. A proper fit of the aftermarket alloy impeller, along with the excellent large GG radiators, make for a bulletproof cooling system.

The cover will groove first, you will be surprised what damage high density plastics can do to soft aluminum when they touch in the right (wrong) conditions.